Christiane Sampaio de Souza

Chlorophyll a and nutrient distribution around seamounts and islands of the tropical south-western Atlantic

Data collected on two large-scale surveys around the seamounts and islands off north-eastern Brazil during 1997 and 1998 provided information on the distribution of Chlorophyll a and inorganic nutrients. During both surveys, the concentrations of Chlorophyll a and nutrients were highly patchy. The highest measurement of Chlorophyll a was 3.91 µg L–1 during 1997. A wide range of nutrient concentrations were found, from undetectable values to a maximum of 17.52 µm L–1 (Si), 1.37 µm L–1 (PO4), 10.02 µm L–1 (NO3) and 0.72 µm L–1 (NO2). In 1998, concentrations of Chlorophyll a and nutrients (nitrite and nitrate) were far more uniform, with Chlorophyll a concentrations lower and phosphate concentrations generally higher than in 1997. Topography–flow interaction on thermohaline structures was observed around Saint Peter and Saint Paul Archipelago and in the Fernando de Noronha Chain, creating a patchy pattern around the island and seamounts. Nutrients exhibited an inverse linear relationship with temperature and salinity and an exponential decay relationship with Chlorophyll a.

Distribution and abundance of carangidae (Teleostei, Perciformes) associated with oceanographic factors along the northeast brazilian exclusive economic zone

This work had as objective to study the distribution and abundance of the Carangidae larvae and to analyze the influence of the hydrological (temperature and salinity) and biological factors (phytoplanktonic biomass and zooplanktonic biomass), on the space and temporal distribution of the larvae. Ichthyoplankton was collected during four expeditions from the Northeast Exclusive Economic Zone. Six species (Trachurus lathami, Decapterus punctatus, Chloroscombrus chrysurus, Selene setapinnis, Selene vomer and Elagatis bipinnulata) and Caranx- Carangoides complex were identified. D. punctatus was the species most abundant (52% of the total), with higher abundance during the Period 3, while the Period 2 was the period of low abundance. C. chrysurus was the second species in abundance representing 30% of the total of carangid. This species had higher abundance during the Period 2 and the Period 1. However, in Period 3 abundance were lesser. The third species in abundance was T. lathami that corresponded 8% of the total of carangid larvae. S. setapinnis, S. vomer and E. bipinnulata were the species less abundant, representing together 2% of the total identified larvae. The larvae of Caranx- Carangoides complex represented 9% of the carangid total.

Relationship between spatial distribution of chaetognaths and hydrographic conditions around seamounts and islands of the tropical southwestern Atlantic

Relationship between spatial distribution of chaetognaths and hydrographic conditions around seamounts and islands off Northeastern Brazil were analyzed from 133 oceanographic stations during the months of January - April of 1997 and April - July of 1998. Oblique zooplankton tows, using 50 cm diameter Bongo nets with 500µm mesh with a flowmeter to determine the filtered volume, were carried out to a maximum of 200m depth. The Superficial Equatorial Water, which had a salinity > 36 PSU and temperature > 20°C, occupied the top 80 to 200m depth. Below this water mass was the South Atlantic Central Water with salinity ranging from 34.5 to 36 PSU and temperature from 6 to 20°C. The community of chaetognaths showed six species: Pterosagitta draco, Flaccisagitta enflata, Flaccisagitta hexaptera, Pseudosagitta lyra, Serratosagitta serratodentata, and Sagitta helenae. Of these species, F. enflata was the most abundant (32.05% in 1997 and 42.18% in 1998) and the most frequent (87.88% in 1997 and 95% in 1998) during both periods. A mesopelagic specie was identified (P. lyra). This specie was more abundant in 1997 (3.42%), when the upwelling was more intense. P. lyra occurred in 22% of the samples during 1997. The abundance of F. enflata, an epiplanktonic species, increased, associated with greater water-column stability.

Seasonal changes in the distribution and abundance of marine cladocerans of the Northwest Alboran Sea (Western Mediterranean), Spain

The annual cycle of marine cladocerans was studied over six years from 1994 to 1999 within the frame of the monitoring Project ECOMALAGA at a nine stations in the NW of the Alboran Sea, with the aim of assessing seasonal patterns and interannual trends in distribution and abundance of marine cladocerans. Seven species (Penilia avirostris, Evadne nordmanni, Evadne spinifera, Pseudoevadne tergestina, Pleopis polyphemoides, Podon leuckarti and Podon intermedius) were detected in the northwest Alboran Sea. Total cladoceran relative abundance varied from 0 to 89 % of the total cladocerans. The abundance of cladocerans was higher in summer-autumn than in winter-spring (7012 - 4711.100 and 743 - 217.100m-3 , respectively). The species composition was very different in terms of seasonality. P. polyphemoides, P. leuckarti and P. intermedius appeared mostly during the spring. P. tergestina, E. spinifera and E. nordmanni predominantly occurred during the winter. P. avirostris occurred mostly during the summer and autumn.

Relación entre las masas de agua y la composición y distribución de las larvas de peces en el mar de Alborán (Mediterráneo occidental) y estrecho de Gibraltar

En este estudio se analizan las relaciones entre la composicion y distribucion de las larvas de peces y los cambios interanuales de las masas de agua en el mar de Alboran y Estrecho de Gibraltar. Entre los taxones dominantes solamente dos taxones costeros (Sparidae y Cepola rubescens) y cinco taxones oceanicos (Ceratoscopelus maderensis, Maurolicus muelleri, Benthosema glaciale, Hygophum benoiti y Capros aper), estuvieron presentes en las dos prospecciones estivales. A nivel de estacion de muestreo, los resultados mostraron notorias sustituciones interanuales, tanto en el taxon dominante, como en la masa de agua. Los dendrogramas reflejaron cambios espacio-temporales en las comunidades larvarias neriticas / oceanicas y mostraron una diferente zonacion horizontal: particion latitudinal en 1993 y longitudinal en 1994. Estos resultados indican que la estructura de las asociaciones larvarias es regulada por los cambios en la hidrodinamica local

Tendencias estacionales y espaciales en la comunidad mesozooplanctónica en una serie temporal plurianual en el noroeste del Mar de Alborán, España

El ciclo anual del mesozooplancton se estudio a lo largo de nueve anos, desde 1992 a 2000, en nueve estaciones ubicadas en el noroeste del Mar de Alboran, con el objetivo de discernir patrones estacionales y tendencias interanuales en la biomasa, composicion y densidad. Las densidades maximas del zooplancton fueron observadas en verano y otono, mientras que los minimos del zooplancton fueron observados en invierno. Los copepodos fueron el grupo mas abundante en invierno, primavera y otono, mientras que en el verano los cladoceros fueron los dominantes seguido por los copepodos. El predominio de cladoceros en verano es basicamente debido a la alta abundancia de Penillia avirrostis. El estudio de tendencias demostro que la abundancia relativa de copepodos aumento en el periodo del estudio, aunque este aumento solamente ha sido significativo en las estaciones occidentales, donde es mas elevada la influencia del agua atlantica. A escala interanual, la biomasa y la densidad registraron una tendencia creciente a lo largo del periodo de muestreo. La diversidad de mesozooplancton mostro una tendencia decreciente. La densidad de Copepoda mostro una disminucion con la temperatura mientras que Cladocera mostro una correlacion positiva. A pesar de estas variaciones interanuales, las distintas fases del ciclo anual y la presencia de varias especies planctonicas fueron notablemente regulares.

Composition of Trichiuridae and Gempylidae larvae (Teleostei) and their association with water masses in the Southwest Atlantic Ocean

Composition of Trichiuridae and Gempylidae larvae (Teleostei) and their association with water masses in the Southwest Atlantic Ocean In this paper the relationship between temporal changes in the occurrence of water masses and Trichiuridae and Gempylidae larvae composition and distribution in the Southwest Atlantic ocean were analysed between 25° and 40° S. Ichthyoplankton was collected during the three expeditions of the Subtropical Convergence Project: Winter and Spring 1977, Autumn 1978 and Summer 1981, realized in the Southwest Atlantic waters. Oblique tows were conducted using a Hensen net with 250 μm mesh size. Steep salinity and temperature gradient were found, where the river outflows from La Plata river (Argentina) and Patos Lagoon (Brazil) met the Tropical Water over the continental shelf between 32 and 36° S. We examined 524 Hensen-net samples that contained about 283 larvae from five species of Trichiuridae and Gempylidae. The most abundant and frequent specie were Trichiurus lepturus Linnaeus 1758 and Diplospinus multistriatus Maul 1948. The mesopelagics species D. multistriatus, Nealotus tripes Johnson 1865 and Lepidopus altifrons Parin&Collette, 1993 were associated with Tropical Water. The benthopelagic T. lepturus and the epipelagic Thyrsitops lepidopoides (Cuvier 1832) were associated mainly with Coastal Water and Subtropical Shelf Water.

The influence of oceanographic conditions on the spatial and temporal patterns of Pleuronectiforms larvae (Teleostei) in the equatorial Atlantic Ocean

In this study, we analyzed the composition, distribution and abundance of Pleuronectiform larvae in relation to abiotic factors (temperature and salinity) and biotic factors (phytoplanktonic and zooplanktonic biomass) in the equatorial Atlantic Ocean. The working hypothesis was that the composition and distribution pattern of Pleuronectiform larvae species present differences between the areas studied according to the hydrographical environment/factors analyzed. Ichthyoplankton was collected during Period: 1 (August - October 1995), 2 (January - April 1997), 3 (April - July 1998) and 4 (September - December 2000), in the equatorial Atlantic Ocean. We examined 562 Bongo-net (500 μm) samples that contained 719 Pleuronectiform larvae belonging to three families: Bothidae (Bothus ocellatus and Engyophrys senta), Paralichthyidae (Syacium papillosum, Citharichthys spilopterus and Citharichthys sp.) and Cynoglossidae (Symphurus sp.). The Pleuronectiform larvae accounted for 4% of total fish larvae and occurred at 37% of the oceanographic stations. B. ocellatus was the species with the highest relative abundance (70%), the greatest value occurring during Period 3 (77%), whereas the lowest relative abundance (57%) was recorded in Period 1. S. papillosum was the species presenting the second highest relative abundance (14%), with higher values during periods 1 and 4. The results demonstrated that environmental factors influence the distribution and abundance of Pleuronectiform larvae so that each species occurs in a more favourable period and place for spawning and growth. B. ocellatus was related to warmer waters and greater phytoplanktonic and zooplanktonic biomass, while S. papillosum occurred in saltier waters and at lower temperatures.